Identifying optimized conditions for developing dewatered alum sludge-based photocatalyst to immobilize a wide range of dye contamination

Abstract

In the current investigation, the removal of Levafix Fast Red CA (LFR) and Levafix Amber CA (LA) azo-dyes from aqueous media using the Fenton/adsorption processes has been carried out. The water treatment by-product, namely alum sludge (AS), was successfully collected and calcined to various temperatures, i.e., 400, 600 and 800 °C, then tested for use as a catalyst in the Fenton/adsorption processes. Fourier transform infrared (FT-IR) transmittance spectrum analysis and Transmission electron microscopy techniques (TEM) were applied to investigate the structural and morphological properties of such a catalyst. The results displayed that the calcined AS at 400 °C (AS400) showed the best photocatalytic activity under ultraviolet illumination and sunlight irradiation. The results indicated that the adsorption/Fenton’s oxidation systems are efficient for treatment and eliminating such types of reactive dyes. The oxidation reaction using Fenton’s reagent reached 99.9 and 86% removal for LFR and LA dyes, respectively. The operating conditions revealed that the reaction was maximized at the operational parameters of 1 g/L and 800 mg/L for AS400 and H2O2 at acidic pH (3.0). The process of single dyes was studied either from thermodynamic and kinetic viewpoints and the data exhibited that the reaction is followed a pseudo-second- order kinetic model and an exothermic reaction nature. The practical application of such byproduct waste used as a photocatalyst source through using natural solar radiation introduces an industrial ecology approach in treating dye effluents for safer environment.